Such means is known from German patent 2 702 750. According to this known means the spindle is pivotally supported at two sliding shoes which are guided in corresponding posts. The spindle foot includes a supporting plate having at its upper and lower end springs which are supported at spring disks engaging the inner side of the post.
According to such a shoring means the spindle can be pivoted relative to the post at a certain angle so that the shoring plates with the posts can be successively and alternately lowered on both sides of the trench which is to be excavated. If one side of the shoring means is located lower than the other side, an inclined position of the spindle results so that the lower or upper spring is correspondingly loaded or unloaded. Such an inclined position of the spindle necessarily causes an inward movement of the two oppositely located posts so that the shoring means is inwardly moved towards the middle of the trench. Accordingly, with the provision of two spindles located one above the other a parallelogram results from a rectangle. Through the inward movement of the shoring means the ground settles so that during the next lowering on one side, according to which the spindle parallelogram is again transformed into a spindle rectangle, it has to be worked against an increased ground pressure, i. e. the settled ground has to be again pressed away for attaining the normal trench width. This movement brings along an increased loading of the posts, shoring plates and spindles.
From European patent 0 095 193 a shoring means is known according to which a spindle or shore is provided with curved front sides which are supported at a corresponding post by means of pad-like resilient means. The respective spindle feet are pivotally supported at the posts. Upon pivoting of the spindle relative to the post the pad-like resilient means are more and more compressed so that their spring stiffness increases. Since, according to this means a fixed pivot point of the spindle is provided at the post either, upon an inclined position of the spindle relative to the post, a corresponding inward movement of the post results which brings along a reduction of the trench width together with a corresponding settling of the ground. It is but proposed in European patent 0 095 193 to support the spindle at the post by means of an elongated hole, however, by the provision of such an elongated hole it is to be achieved only slight pivotal movements of the spindle about a vertical axis as well as movements in axial direction of the spindle. Accordingly, a co-movement of the post cannot be excluded in this case either.